Speculation about who will rule Saudi Arabia in the future is mounting after the surprise February 1 appointment of Prince Muqrin bin Abdulaziz as second deputy prime minister, a post long viewed as "crown prince in waiting." The unexpected move puts a spotlight on the complicated politics and procedures surrounding Saudi succession.

BACKGROUND

Prince Muqrin is the youngest surviving son of the late Ibn Saud (a.k.a. King Abdulaziz), the founder of Saudi Arabia. He is now the third most powerful person in the kingdom, behind King Abdullah (who also serves as prime minister) and Crown Prince Salman (the deputy prime minister). Both of these men are ailing, however: Abdullah (age 90) is rarely seen standing upright and has a limited attention span, and Salman (77) has dementia. In comparison, Muqrin (70) appears to be in good health.

His appointment has confused analysts because he was sacked as head of the Saudi General Intelligence Directorate just last July. Although no reason was given for that decision, he was assumed to lack the mettle needed for undermining the pro-Iranian Assad regime in Syria, where Riyadh is competing with its Gulf rival Qatar for influence and control of jihadist fighters. This assumption may have been mistaken.

Additionally, the change comes just three months after Muqrin's nephew, Prince Muhammad bin Nayef, was elevated to the important position of interior minister (equivalent to the U.S. secretary of homeland security), seemingly setting Muhammad up as a potential future king. Indeed, during a visit to Washington last month, Muhammad met with President Obama in the White House, a privilege not normally accorded to foreign officials of that rank and therefore widely perceived as conferring U.S. approval of his regal prospects.

COMPLICATED SUCCESSION

In the past, the Saudi line of succession has been from brother to brother among the sons of Ibn Saud, in contrast to the father-son method seen in most other monarchies. The main qualification has been seniority in age, though some princes have been passed over due to incompetence or unwillingness to take the role. One consequence of this system has been shorter reigns for most of the kings since Ibn Saud, as his sons are increasingly old and often ailing when they assume the throne. For years, many have argued that the crown should pass to the next generation, the grandsons of Ibn Saud -- hence the excitement following Prince Muhammad's meteoric rise to interior minister. But the royal family has never been able to agree on when this shift should happen, and which line should be chosen.

Muqrin's new status also challenges another presumed succession principle: that the king's mother should be from a Saudi tribe. Muqrin's mother was Yemeni, and it is not even clear that Ibn Saud was married to her.

Indeed, Ibn Saud's domestic arrangements in the 1920s to 1940s are central to understanding current succession politics. By the time he died in 1953, he had fathered forty-four sons, thirty-five of whom survived him. This feat was accomplished by having twenty-two wives, though in keeping with Islamic tradition he was never married to more than four at a time.

Some historians -- and all Saudi officials -- emphasize that these marriages and the resulting offspring were vital to uniting the tribes and stabilizing the nascent kingdom. The reality is more nuanced: one well-researched work ("The House of Saud" by David Holden and Richard Johns) notes that in addition to four wives, Ibn Saud typically had four favorite concubines and four favored slave girls "to complete his regular domestic team." Muqrin's mother, usually identified as "Baraka the Yemeni," was presumably in one of the latter categories.

Ibn Saud clearly regarded Muqrin as a full son. The question now is the attitude of Muqrin's sixteen half-brothers and his many nephews, who might regard their own pedigrees as superior. Apart from age, the other criteria for becoming king are experience, acumen, popularity, mental stability, and the status of one's maternal uncles (which indicates whether one's mother was a slave or concubine).

CURRENT ROYAL FACTIONS

Muqrin himself has no recorded full brothers, a status he shares with King Abdullah, which might explain the perceived bond between the two men. Fraternal alliances have been significant in royal politics. For decades, the so-called "Sudairi Seven" -- full brothers Fahd, Sultan, Abdulrahman, Nayef, Turki, Salman, and Ahmed, all born to Hassa al-Sudairi -- were a crucial constituency. Although the deaths of King Fahd and Crown Princes Sultan and Nayef depleted the bloc's strength, Crown Prince Salman continues to lead the faction despite his dementia, propped up by his own sons and Sudairi nephews.

Assessing the combined strength of these nephews presents its own challenges. Muhammad's elder brother Saud bin Nayef was recently named governor of the oil-rich Eastern Province, but he replaced another Sudairi nephew, Muhammad bin Fahd. In addition, one of Salman's sons has been appointed governor of Medina province. Clearly, the Sudairi nephews possess the experience and ability to remain a significant force in palace politics.

LEGAL AMBIGUITY

Saudi laws and official statements fail to clarify how the current situation will evolve. The 1992 Basic Law of Governance (http://www.saudiembassy.net/about/country-information/laws/The_Basic_Law_Of_Governance.aspx) merely states that "rule passes to the sons of the founding king and to their children's children." The principal qualification is to be "the most upright among them," and this vague criterion is not defined.

In 2006, King Abdullah established an Allegiance Council of princes to help guide future succession. Yet the scope of its role is ambiguous: the council was not involved in the selection of new crown princes to succeed Sultan (who died in 2011) or Nayef (who died last year). In both cases, Abdullah chose the replacement and the council merely approved it. The Allegiance Council Law does include a mechanism to replace the king and crown prince if they are incapable of carrying out their duties for health reasons; the kingdom is arguably nearing this point.

Legally, Muqrin's new post -- second deputy prime minister -- exists only to provide an additional person to chair the weekly Council of Ministers meetings; the position has therefore gone vacant at times. According to the Law of the Council of Ministers, these meetings "are presided over by the king, who is the prime minister, or by a deputy of the prime minister." It is therefore by convention, not law, that the second deputy prime minister is destined to be crown prince.

Whether any of the above legal documents or bodies will actually be used to determine Saudi Arabia's future kings or crown princes is a matter of conjecture. There is nothing to stop the king from abolishing the Allegiance Council and establishing alternative procedures. Meanwhile, various succession scenarios are swirling through the kingdom and the wider Arab world. One is that Muqrin will become king and appoint Abdullah's son Mitab as his crown prince, thereby cutting out Sudairi challengers. Although rivalries within the House of Saud traditionally play out behind palace walls, the increasingly high stakes suggest that the rest of the world may get a glimpse of the coming maneuvers.

Simon Henderson is the Baker fellow and director of the Gulf and Energy Policy Program at The Washington Institute.